Cones mark a new entry installed recently at a grain terminal at the Port of Portland for access in case of a strike or lockout.Brent Wojahn/The Oregonian

The West Coast longshore union, fresh from victory in Portland contract talks Saturday, wants an extension of separate Northwest grain negotiations to head off a strike or lockout this week.

A spokeswoman for the International Longshore and Warehouse Union said Monday that members don't want to strike terminals that handle a quarter of U.S. grain exports. The union has asked the owners of six terminals in Portland, Vancouver and the Puget Sound to extend a midnight Wednesday deadline imposed by employers Nov. 16 in a contract offer they termed final.

Union spokeswoman Jennifer Sargent told The Associated Press that union leaders feel the talks are not at an impasse and have proposed additional negotiation dates. The earliest the union could hold a vote by the membership, she said, is Dec. 21 and 22.

Terminal owners issued no immediate response Monday. But all signs are that the coalition of four companies is preparing for a lockout or strike as soon as Thursday.

If either occurs, the employers plan on hiring workers to replace longshoremen loading vessels with wheat, corn and soybeans. Union members would protest on land and in boats, according to the U.S. Coast Guard.

Longshoremen have worked without a contract since theirs expired Sept. 30. A federal mediator tried to move the two parties toward agreement. But the employers demand big concessions in working conditions similar to those made by the union earlier this year at a Longview, Wash., grain terminal where violence and arrests occurred.

A lockout or strike would affect terminals that handle about $10 billion in annual trade, including half the nation's wheat exports. Economic effects would dwarf those expected from a strike averted Saturday at the Port of Portland.

In those talks, 25 marine guards in longshore union Local 28 got the Port to promise them its security work at two terminals through June 2015.

But in a lucky turn of events for the Port, a mishap in Canada delayed the Hanjin Geneva, meaning the container vessel was able to show up in Portland after all Monday.

The 68,000-ton ship, heading from South Korea to Canada Tuesday, ran aground on a sandbar off Prince Rupert after its coastal pilot tried to avoid a small fishing boat.

Therefore the ship arrived late in Seattle, giving Hanjin managers time to reverse their decision to bypass Portland. The switch avoided stranding exports in Portland and trucking imports from Seattle.

"The delay was helpful in this case, yes," said Jeff McEwen, Hanjin's Portland manager. "We wanted to come to Portland if at all possible."